ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
Early in the process of spore formation in Bacillus subtilis, asymmetric cell division produces a large mother cell and a much smaller prespore. Differentiation of the prespore is initiated by activation of an RNA polymerase sigma factor, σF, specifically in that cell. σF is controlled by a regulatory cascade involving an anti-sigma factor, SpoIIAB, an anti-anti-sigma factor, SpoIIAA, and a membrane-bound phosphatase, SpoIIE, which converts the inactive, phosphorylated form of SpoIIAA back to the active form. SpoIIE is required for proper asymmetric division and much of the protein is sequestered into the prespore during septation. Importantly, activation of σF is dependent on formation of the asymmetric septum. We have now characterized this morphological checkpoint in detail, using strains affected in cell division and/or spoIIE function. Surprisingly, we found that significant dephosphorylation of SpoIIAA occurred even in the absence of septation. This shows that the SpoIIE phosphatase is at least partially active independent of the morphological event and also that cells can tolerate significant levels of unphosphorylated SpoIIAA without activating σF. We also describe a spoIIE mutant in which the checkpoint is bypassed, probably by an increase in the dephosphorylation of SpoIIAA. Taken together, the results support the idea that sequestration of SpoIIE protein into the prespore plays an important role in the control of σF activation and in coupling this activation to septation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1365-2958.1999.01543.x
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